1. Field of the Invention
The present invention relates to a filter element and a process for manufacturing the same for utilization in an air cleaner for an internal combustion engine of an automobile.
2. Description of Related Art
With a view to improve the filter area and the strength, to reduce the price and to facilitate the material recycle, a variety of filter elements have been proposed conventionally.
In Japanese Patent Application Laid-Open No. 51-85561, for example, there has been disclosed a technique by which a cup-shaped filter portion and a flange portion around the outer periphery of the filter portion are formed of paper. In this prior art, moreover, the filter portion is given a necessary strength by forming thick and thin portions.
In Japanese Patent Application Laid-Open No. 6-57293, on the other hand, there has been disclosed an element in which a wavy sheet filter material and a cotton filter material are laminated. According to this technique, it has been proposed to form a flange portion for supporting the filter, by closing the side faces of the wavy sheet with the cotton filter material and by compressing the cotton filter material.
In Japanese Patent Laid-Open No. 6-315604, on the other hand, there has been a proposal for closing the wavy sheet side faces by pressing down the waves at the side faces of the wavy sheet filter material.
In European Patent Publication No. 049016B1, on the other hand, there has been a proposal for adhering or welding a separate flange portion to a wavy sheet filter material.
These techniques are effective for facilitating the recycling because the wavy sheet filter portion and the enclosing portion are made of a similar material.
According to the technique of Japanese Patent Application Laid-Open No. 51-85561, however, it has been difficult to enhance only the strength of the flange portion. According to the technique of Japanese Patent Application Laid-Open No. 6-57293, on the other hand, there is a problem that the manufacture process is complicated because two kinds of different materials, i.e., the wavy material and the cotton-shaped material are required. Because of the construction having the cotton-shaped filter material positioned upstream, moreover, another problem is that it is difficult to retain a sufficiently wide filter area. Still moreover, since the flange portion is formed by pressing only the wavy sheet filter material and the cotton-shaped filter material to be doubly laminated, still another problem is that a high rigidity cannot be obtained from the flange portion.
According to the technique of Japanese Patent Application Laid-Open No. 315604/1994, on the other hand, the flange portion for supporting the filter element in the housing has to be separately prepared and adhered.
According to the technique of European Patent Publication No. 049016B1, on the other hand, since the flange portion is separately prepared and adhered, there has been a drawback in the complicated manufacture process and in the increase in the number of parts.